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[[centered]][[bold]][[hand-underlined]]Super-Conducting Copper[[/hand-underlined]][[/bold]][[/centered]]

A Tantalizing Laboratory Achievement Which May Lead to Industrial Economies

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It is told how Lord Kelvin, the famous scientist, in 1857 found that copper wire used in cable manufacture differed much in conductivity, and urged that trans-atlantic cables be made of high-conductivity copper-chemically pure metal, capable of transmitting current with much less loss than occurred in the usual, more or less impure, copper. This was one of the early applications of research to finding better electrical conductors.

From that day to this, pure copper has been used almost exclusively for electrical transmission. The only known material with higher conductivity than pure copper is silver, a metal too costly for use in line wires.

But in spite of this settled practice, interesting questions remained. Why is silver more conductive than copper? Why is copper, next to silver, more conductive than all other metals? Is its conductivity absolutely a fixed thing, or is it susceptible of increase by special treatment?

A small increase in the conductivity of commercial copper would have great value. An increase of even 10 per cent would release for other fields an enormous tonnage of copper now used for transmitting power. The economic radius of all existing transmission systems would be increased 10 per cent, increasing by 21 per cent the area served, or the underground cable subways of cities, so many of which are taxed to capacity with their loads of today, could without enlargement carry additional loads to ten per cent.

So when Dr W P Davey, of our Schenectady research laboraory, found by calculations based on the arrangement of the copper atoms which the X-rays revealed that copper composed of a single crystal should have a conductivity of 14 per cent greater than ordinary copper, greater than that of silver, possibilities of tremendous scientific interest were disclosed. In order to check his calculations, Dr. Davey proceeded to devise apparatus for producing large single crystals of copper The single crystals were made by very gradually heating and cooling pure copper in an electric furnace. When molten metal is quickly cooled, very small crystals are formed, if the metal is cooled slowly,
the crystals are larger Dr Davey cooled the melt so slowly that only one crystal was formed, and that included all of the metal. By this method he was able to produce single crystals three-fourths of an inch in diameter and six inches long, and one that is fourteen inches long

The conductivity of these crystals was then measured, and, although the quantities involved were only 6,-1 [[paper torn - missing text]]
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000th of a volt and 18-1,000,000ths of an ohm, measurements by different methods were made which checked within one quarter of one per cent. The measured conductivity was 113 per cent that of pure polycrystalline copper, or within one per cent of its calculated value.

In a crystal, the atoms--the unit particles of the substances--are built up in regular fashion. The crystals of copper, for example, are made up of very tiny cubes, with atoms of copper at the corners and centers of the faces of each unit. The larger crystals grow in such a direction that the atoms are arranged in columns along the length of the crystals. It is this regular arrangement of the atoms which, it is believed, gives to the single crystals their superior conductivity when compared with ordinary (polycrystalline) copper, in which the crystals are small and the arrangement of these small crystals quite chaotic.

There is reason to believe that the conductivity of copper crystals along another axis from that measured may be even 60 per cent greater than the value for pure copper, but the growth of single crystals along this other axis has not yet been brought under control.

Unfortunately, there is no immediate prospect of utilizing commercially this newly discovered high conductivity, for the single crystals are very delicate and difficult to manufacture.

One of the first facts discovered about single-crystal copper was that the speciments could be bent double with one finger, but that strength was required to straighten them out afterwards. A crystal of the same size of a lead pencil, if given a jerking motion, bends like a stick of soft wax. Having been once bent, however, it acquired the properties of ordinary copper, for the bending has transformed the large crystal into a mass of smaller ones.

(Note: This article, the first of a series dealing with the interesting results of recent research, is printed through the cooperation of the Engineering Foundation, New York)
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[[handwritten text]]From the May 7, 1926 Erie Works News[[/handwritten text]]
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